US2412955A - Telegraph switching system - Google Patents

Description

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TELEGRPH SWITCHING SYSTEM A Filedsept. 18, 1943 15 Sheets-Sheet 16 :L E-Mp Illl w M. BAco/v NVNTORS' w R. You/ve JR.

A T TORNE 3" Patented Dec. 24, 1946 2,412,955 TELEGRAPH SWITCHING SYSTEM York, N. Y., and William R.

Walter M. Bacon, New

Young, Jr.,

Telephone Laboratories,

Summit, N. J., assignors to Bell Incorporated, New

York, N. Y., a corporation of New York Application September 18, 1943, Serial No. 502,944

17 Claims.

This invention relates to communication systems and more particularly to automatic telegraph switching systems in which messages are automatically directed and routed to stations oi ultimate destination under control of certain predetermined signals or code combinations usually preceding each message.

The object of the present invention is to provide an improved telegraph system employing less apparatus than comparable systems of the prior art and at the same time expediting the transmission of messages through the system.

In accordance with an exemplary embodiment of the invention, the system disclosed in United States patent application. of Branson et al., Serial No. 448,878, led June 27, 1942*, has been improved in order to expedite the transmission of messages through the system and at the same time require less apparatus and hence less sources of trouble and less equipment to maintain, thus improving the service and at the same time reducing the cost per message. In accordance with the system disclosed in said Branson et al. application, messages are transmitted from outlying stations to a central switching station. At the central switching station the messages intended for other outlying stations are stored in a tape by means of a reperforator. The tape then controls the transmitter which transmits the message through selective switching equipment to a second reperforator associated with a line extending towards the station of ultimate destination of the message. Thereafter the second tape controls a transmitter 'which transmits the message over the line' extending towards the station of ultimate destination.

In accordance with the present invention the second storage of the message is dispensed with except when the line extending towards the station of ultimate destination is employed for the transmission of another message over' that line. Hence during periods of light traic the messages are not stored a second time. Instead the messages are immediately transmitted over the line extending towards their stations of ultimate destination. However, when the trailc over the line becomes heavier many messages will be directed to a storage device associated with said line. Thus during a considerable portion of the time the second storage of the message is dispensed with as well as the equipment necessary for accomplishing this second storage. However, when the line 'becomes more heavily loaded as is usual during certain hours of the day many of the messages will be stored a second time and` await their turn for transmission over the outgoing line to which they have been directed.

A feature of this invention relates to switching circuits and apparatus which will select an outgoing line if that line is idle and alternatively and automatically select a storage device and transmit messages thereto if the line had been previously selected by the selecting equipment and a message is in the process of being transmitted thereover.

In addition, the system is arranged to provide numerous other tests, alarm, and other features as disclosed in said above-identified application of Bransonet al., all these being incidental to message transmission and in the nature of auxiliary apparatus.

The foregoing objects and features of the present invention, the novel features of which are specically set forth in the claims appended hereto, may be more readily understood from the following description when read with reference to the attached drawings in which:

Fig. 1A shows the manner in which Figs. 2, 3 and 4 should be arranged adjacent one another to show in outline form the various circuits and equipment of an exemplary system in accordance with the present invention as well as illustrate the routes of messages through the system;

Fig; 1B shows the manner in which Figs. 5 through 17, inclusive, should be arranged adjacent one another to show the circuit arrangements in detail of one exemplary form of the invention;

Figs. 2, 3 and 4 show in outline form a typical system embodying the present invention; and

Figs. 5 through 17, inclusive, when arranged as shown in Fig. 1B, show in detail the various circuits and equipment comprisingandcooperating with the present invention.

Referring now to Figs. 2, 3 and 4 when arranged as shown in Fig. 1A, Fig. 2 shows two typical party lines and the station and control equipment associated therewith. One party line is designated 2 I0 which comprises a receiving channel 2l i and a transmitting channel 2 I2. Similarly, party line 260 comprises a receiving channel 26| and a transmitting channel 262. Both transmitting and receiving channels are illustrated in Fig. 2 and also Fig. 3 by means of telegraph lines or conductors. It is to be understood, however, that these lines or channelsmay include any type 0f telegraph transmission equipment normally employed for the transmission of telegraph signaling pulses or code combinations of pulses.

55 These lines or channels may, for example, include open wire lines, cable lines, channels of voice frequency or high frequency carrier current systems, radio systems, time division multiplex systems or telegraph channels of composite telephone and telegraph transmission systems or of any other type of pulse transmission channels or systems suitable for the transmission of signaling pulses such as employed in telegraph systems. The various party lines and channels thereof may include or comprise any or all of the foregoing types of transmission systems or any or all combinations of such types of transmission systems.

The transmission systems of the various types comprising the party lines operate in their usual and Well-understood manner so a description of the operation thereof need not be included herein because it would serve no useful purpose and only tend to obscure the other elements and features of the present invention.

Each of the party lines shown in Fig. 2 extends to a plurality of outlying subscriber or Way stations. It is to be understood also that it is within the scope of this invention to extend lines individually from one or more of the outlying stations to the central switching exchange. In .this case certain of the control equipment associated with each of the party lines need not be provided as will be readily apparent .to those skilled in the art.

Each of the lines which extends to more than one outlying station is provided with control equipment located at or near the outlying stations of the party line. Control equipment may be provided which is individual to each of the outlying or way stations in case the way stations are rather widely separated or the control equipment may be provided common t0 a group of outlying stations which are `located more closely together. In addition, certain of the control equipment may be individual to certain outlying stations, while other control equipment provided for the same party line may be common to a plurality of the outlying stations.

As shown in Fig. 2, three separate and distinct sets of switching and controlling circuits, sometimes referred to as a secondary switching center, are associated with each of the party lines. For example, party line 2 l 0 extends to the switching and control circuits or secondary Yswitching centers 2|3, 2|4 and 2|5. The control equipment 2|4 is individual to station 2l9. Control equipment 2|5 is common to stations 2 i6, 2|1 and. 218,

-while control equipment 2l3 is common to stations 225 to 224, inclusive. Each of the outlying stations is provided with a receiving instrument, transmitting equipment, and control equipment. In the specific system described herein, the transmitting equipment comprises a keyboard perforator for perforating paper tape in accordance with the signals to be transmi-tted and a tape controlled transmitter for transmitting signals in accordance with the perforations in the tape. For example, at station 2|6 the receiving instrument and the keyboard Vperforator is illustrated diagrammatically anddesignated 22,5 in Fig. 2, the transmitting distributor is designated 235, while the con-trol equipment is designated 236. Similar equipment is provided at the other stations. In

addition, -station 2I9 is provided with a receiving recorder or reperforator for again perforating tape in accordance with messages received from the system. This reperforator is provided at 'those stations at which other telegraph lines or circuits terminate so that the messages intended Cil `vice 422.

4 for stations connected to these other lines may be recorded at station 2|9 and later automatically transmitted over the proper line without requiring the time of an operator to retransmit the message.

In order to transmit messages over this system, the attendant or subscriber at the outlying or way stations perforates messages in paper tapes for later transmission over the system. Preceding each message, an address or group of switching signals is perforated in the tape and following each message an end-of-message or disconnect signal is also perforated in the tape. Following the end-of-message signal the subscriber may perforate any address signal followed by another message intended for the station designated by the address. Following this message and each of the messages, the operator will then perforate a disconnect signal in the tape. Furthermore, the operator or attendant will usually perforate an end-of-transmission signal in the tape after the disconnect signal following the last message available for transmission from the station then transmitting.

The attendant or operator at the outlying station will then insert a tape in the transmitter for transmission over the system. At a later time the transmitter is started under the control of an operator or switching circuits at the central switching station. Thereafter the messages are transmitted to the central ,switching station and recorded thereat.

The circuits at the central switching station are illustrated in Figs. 3 and 4. Fig. 4 shows the originating position at the central switching station comprising a keyboard perforator 4H, a monitoring receiving instrument 4|0, transmitter and transmitting distributor 4I2, control relays 4l3 and a director circuit 4|4. Fig. 4 also shows a miscellaneous intercept circuit 421 and a receiving reperiorator 426 and a tape receptacle 425. A willful intercept circuit 424 is also shown. This intercept circuit is provided with a repeating instrument 420 comprising a recorder or reperforator 42| and a transmitting de- A director 423 is also associated with the willful intercept circuit.

Each of the party lines terminating at the switching oice or center is provided with an incoming line circuit 322 and a receiving only ma.- chine 323, a storage repeater 324 and associated transmitter 325. Incoming line circuit 322 causes the messages intended for the central switching station to be recorded on the receiving only receiver 323 and causes the messages intended for other stations of the system to be recorded by the reperforator 3 28. Director circuit 327 is associated with the transmitter 325 and serves to connect the transmitter 325 selectively to any of the lines terminating at the central switching station under control of the address characters preceding each message.

Each of the party lines is also provided with transmitter start circuits, such as 3|0, and outgoing line circuits and equipment for transmitting messages over the party line. The outgoing line circuit associated with party line 2 I0 incorporates control circuits and equipment in accordance with the present invention as will be described hereinafter. Briely, messages directed to stations of party line 2l I are transmitted either directly over the party line or to storage repeaters associated with line 2li under control of Athe director circuits individual to the lines upon which the messages originate for later transmission over the outgoing lines.

' Figs. 2 and 3 also show a trunk circuit 290 comprising two transmission channels 29| and 292 extending to' a distant switching center 295. The terminal equipment associated with the trunk circuits is similar to the terminal equipment associated with each of the party lines as described above.

The operation of the various circuits referred to above is described in detail-in the above-identified copending patent application of Branson et al. Since the respective circuits referred to above forming parts of the systems referred to herein operate in substantially the same manner as described above in said patent application of Branson et al., which patent application has been made a part hereof as if fully included herein, an elaborated description has therefore not been repeated here.

Reference will now be made to Figs. 5 through 17, inclusive, when arranged as shown in Fig. 1B. Fig. 5 shows the subscribers stations and control equipment associated with party line 2H). The subscribers stations and control equipment associated with party line 2H! are shown in substantially the same form as shown in Fig. 2. In addition, the same reference numerals have been employed to designate stations and equipment. Details of typical party lines of this type are described in the above copending application of Branson et al. and also in a patent application of Krecek et al., Serial No. 408,406, iled August 28, 1941, which was issued on January 9, 1945 as Patent 2,366,733, the disclosures of which are hereby made a part of this specification as if fully included herein. Inasmuch as the equipment in the circuits at the subscribers stations as well as the control circuits therefor operates in substantially the same manner as described in the aboveidentified copending applications, detailed operation of these circuits will not be repeated here. Fig. 5 also shows transmitter start circuit 310 as well as the incoming line circuit 322. As described above, incoming messages intended for the central switching center are directed to the receiving only machine H56, while messages intended for other stations of the system are recorded by the reperforator H02.

Inasmuch as the circuits and equipment at the outlying stations and the control thereof in the exemplary system disclosed herein operate in the same manner as described in the above-identified applications of Branson et al. and Krecek et al., they have been shown only in outline form and a detailed description of their operation will not be repeated here. Likewise the transmitter start circuit 3 l 0 as well as the incoming line circuit 322 has been shown only in outline form since these circuits operate in substantially the same manner and cooperate with the other circuits in a similar manner to the manner described in said Branson et al. application. Consequently the detailed description of the operation of these circuits need not be repeated since this information may be obtained by reference to the applications above identified and incorporated herein. However, inasmuch as the director circuit cooperates with the outgoing line circuit in a novel manner and inasmuch as the outgoing line circuit has been materially modified, an exemplary form of these circuits is shown in detail in Figs. 5 through 17, inclusive, and the operation of these circuits will bedescribed in greater detail in order that the operation of the improved circuits as well as theV manner of cooperation between the various circuits may be more readily understood.

In the exemplary system shownin Figs. 2, 3 and 4 only one line of each of the different types oflines disclosedin the above-identified application of Branson et al. is indicated. It is to be` understood, however, that any number of the var-V ious types of lines and their associated equipment may be provided as are required by any one or more of a number of different conditions and requirements encountered in any specific instal.

lation. Likewise equipment associated with only one of the lines is shown modified in accordancev with the present invention in Figs. 2 through 4, inclusive. It will be readily apparent to those skilled in the art, however, that the equipment associated with any one or more of the lines may readily be modified in accordance with the present invention. The amount of equipment and the number of lines and the features provided on each line will vary depending upon the circumstances of each installation. However, lines equipped in accordance with the present inven` tion will cooperate with all the other lines of such an exemplary system.

Likewise Figs. 5 through 17, inclusive, show in detail the circuits associated with only one of these lines. It will be'readily appreciatedv by persons skilled in the art, however, that the equipment disclosed in these gures may be duplicated for additional lines and it may be incorporated without involving invention in any of the other types of line circuits disclosed in said copending applications.

Assuming now by way of example that it is desired to transmit a message from station 2|6 to station 222. The attendant at station 2l6 will perforate the address or switching codes AG one or more times in the tape preceding the message. The attendantv will then perforate the message in the tape after which a disconnect or end-of-message signal comprising a figures signal is followed by an H signal and this in turn is followed by a letters signal. The attendant may perforate additional messages in the tape each preceded by proper address code or signals and each followed`by an end-of-message group of code combinations. After a predetermined number of messages have been perforated in the tape the attendant will perforate an end-of-` transmission group of codes in the tape. Thereafter the tape will be inserted in transmitter 235.

At a somewhat later time the transmitter will be started into operation in response to the operation of the transmitter start circuit 3I0 at the central switching station. Transmitter 235 will then transmit the address codes followed by the message over the transmitting channel -2I2 of party line ZIB.

The operation of the equipment at the central station including the incoming line circuit 322 in cooperation with the receiving printer H56 and the reperforator ,I |02 and the associated circuits in response to the address codes AG preceding the message causes the message to be directed to the selector magnet H03 of the reperforator HB2. Magnet H03 in turn causes the message to be printed upon and perforated in tape H05. The reperforator H02 is arranged to cooperate with the transmitting instrument shown in Fig. 11 so that the transmitting equipment shown in Fig. 11 will transmit the last character recorded inthe tape H05. The details of such a transmitter andreperforator are shown andV described 7 in the above-identified application of Branson et al. incorporated herein and therefore need, not, be repeated here.

Upon the reception'of the address codes A and G by the reperforator I I '2 the increase in supply of tape between the reperforator and the sensing head H00 of the transmitter will cause the sensing head H06 to be rotated in a clockwise direction as seen in Fig. l1 thus permitting contacts H2I to close. The closing of contacts H2I completes a circuit for the operation of relay I 3| 6. Relay |3I6 in turn completes circuits for the operation of relays I3H, I3I'I, I32I and I2I8. The operation of relay I3 I 6 also completes a circuit for the operation of the transmitter magnet IIII. The circuits for the operation of the above relays and magnet are traced in detail in the aboveidentified application of Branson et al. and need not be repeated here. Similarly the circuits for the operation of various of the other relays to be described hereinafter are likewise set forth in detail in said Branson et al. application so that this information will not be repeated at this point.

The operation of magnet IIII withdraws stop latch I'H3 and 'permits shaft H53 to rotate through one revolution. Near the beginning of this revolution the tape is advanced through the sensing head H06 so that the feeler pins will be below the next set of perforations in the tape H05. That is, they will be below the first set of perforations received by the printing reperforator H02. Thereafter arms IIO'I are released and permit the feeler pins to sense the tape to determine the perforations therein. which encounter perforations above them will rise further as viewed in Fig. I1 than those which do not find perforations above them. At a later time after the arms H01 have been fully positioned in accordance with the perforations in tape H135 the transfer cam H20 will cause the transfer members I I 08 to be moved to the left as viewed in Fig. 11 and engage either the upper or lower bifurcated end of the arm I I01 and thus cause the members He to be positioned in accordance with the perforations in tape I |05. The transfer members H08 control intermediate members HIO having a projection H53 which engages a switchl controll member H09 which in turn causes the contacts controlled thereby to be positioned in accordance with the perforations in tape H05.

During the revolution of shaft H53 cam IHS will cause contacts I I I'I to be momentarily closed. The momentary closing of contacts III I completes a circuit for the operation of relay I4I3 which relay operates and completes a circuit for maintaining itself operated under control of relay MI5. Relay I I3 in operating interrupts the operating circuit of release magnet IIII, thus insuring that magnet I HI will release and cause shaft H53 to stop at the end of one revolution.

After the contact members I I 09 have had ample time to position the contacts controlled by them in accordance with the perforations in the tape H contacts III 6 are closed in response to the rotation of cam HI8 on shaft H53. Closure 0f contacts IHS completes a circuit for the operation of the distributor release magnet I |41. Magnet IMI releases a distributor shaft II5I for rotation through one revolution.

During this revolution the transmitting contacts I to 5 are closed in sequence for transmitting a signal code combination in accordance with The pins series with relay MI2.

the setting of the contacts.` controlled by members H09. However, since the contacts I. to 5 0f the distributor are not connected to any transmission circuit at this time, this signal is not transmitting during the revolution of shaft II5I. Near the beginning of the revolution of the shaft, II5I cam H49 causes contacts H50 to close. The closure of contacts H50 completes a circuit for the operation of relay H42.

Under certain circumstances the rst characters received by the reperforator H02 may be switching characters which have already performed their function, may be disconnect characters and certain other characters which are normally discarded by the switching equipment. The contacts controlled by members H09 are arranged to complete circuits through them from ground in response to each of the discard characters. As described in the above-identified aD- plication of Branson et al., these discard characters include the figures, H, letters and Z code combinations or signals. Upon the operation of relay MI2 if the code combination above the sensing pins is one of the discard characters, re lay I3I8 is operated. Near the completion of the revolution of the distributor shaft II5I contacts H50 reopen at which time relay ISIS operates and locks operated in series with relay I4I2.

The operation of relay I 318 in response to a discard character as described above completes a circuit for the operation of relay I4I5. Relay MI5 in operating interrupts the locking circuit of relay MIS and relay I4I3 releases. Relay I4I3 in releasing interrupts the locking circuit of relays I3I9 and MI 2 and permits these relays to release which relays in turn cause the slow release relay I3I8 to release. After a short interval of time relay I3I8 will release and cause relay MI5 to release. The release of relay I 4I5 will again complete a circuit from the transmitter release magnet I II I and the above cycle of operation is` repeated as long as discard characters are presented over the feeler pins of the transmitter.

Following the discard signals recorded in tape H05 the address code of the succeeding message will usually be recorded. As assumed above this address code is AG. When the letter A code combination appears above the sensing pins relay E3I8 will not be operated upon the operation of relay I 4I2 as described above. Near the end of the revolution of the distributor shaft II 5I contacts H50 reopen as described above and permit relay ISIS to operate and lock operated in With relay ISIB released and relay IBIS operated a circuit is completed for the operation of relay I 522.

Relay I 522 in operating interrupts the operating of the slow release relay I 3H. This relay does not, however, immediately release since it is a slow release relay and allows time for certain of the other relays to function before it releases. The operation of -relai7 ,|522 connects the first group of fan or coding relays I5I6 to I52I to the contacts controlled by members H09 thus positioning the relays in accordance with the code combination recorded intape H05. Under the assumed conditions these relays will be positioned in accordance with the letter A signal.

The operation of relay |522 completes a circuit for the operation of relay MI5 which relay operates and in turn causes the release of relays MI3 and MI2 and I3I9. The operation of, relay I5I5 extends a circuit from the winding of relay I322 to a sequence circuit |650. When the

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